title: Pyrolysis of furan in a microreactor.
abstract: A silicon carbide microtubular reactor has been used to measure branching ratios in the thermal decomposition of furan, C4H4O. The pyrolysis experiments are carried out by passing a dilute mixture of furan (approximately 0.01%) entrained in a stream of helium through the heated reactor. The SiC reactor (0.66 mm i.d., 2 mm o.d., 2.5 cm long) operates with continuous flow. Experiments were performed with a reactor inlet pressure of 100-300 Torr and a wall temperature between 1200 and 1600 K; characteristic residence times in the reactor are 60-150 μs. The unimolecular decomposition pathway of furan is confirmed to be: furan (+ M) ⇌ α-carbene or β-carbene. The α-carbene fragments to CH2=C=O + HC≡CH while the β-carbene isomerizes to CH2=C=CHCHO. The formyl allene can isomerize to CO + CH3C≡CH or it can fragment to H + CO + HCCCH2. Tunable synchrotron radiation photoionization mass spectrometry is used to monitor the products and to measure the branching ratio of the two carbenes as well as the ratio of [HCCCH2]/[CH3C≡CH]. The results of these pyrolysis experiments demonstrate a preference for 80%-90% of furan decomposition to occur via the β-carbene. For reactor temperatures of 1200-1400 K, no propargyl radicals are formed. As the temperature rises to 1500-1600 K, at most 10% of the decomposition of CH2=C=CHCHO produces H + CO + HCCCH2 radicals. Thermodynamic conditions in the reactor have been modeled by computational fluid dynamics and the experimental results are compared to the predictions of three furan pyrolysis mechanisms. Uncertainty in the pressure-dependency of the initiation reaction rates is a possible a source of discrepancy between experimental results and theoretical predictions.
authors.affiliation: Center for Combustion and Environmental Research, Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309-0427, USA.
authors.forename: Kimberly N
authors.initials: KN
authors.lastname: Urness
authors.forename: Qi
authors.initials: Q
authors.lastname: Guan
authors.forename: Amir
authors.initials: A
authors.lastname: Golan
authors.forename: John W
authors.initials: JW
authors.lastname: Daily
authors.forename: Mark R
authors.initials: MR
authors.lastname: Nimlos
authors.forename: John F
authors.initials: JF
authors.lastname: Stanton
authors.forename: Musahid
authors.initials: M
authors.lastname: Ahmed
authors.forename: G Barney
authors.initials: GB
authors.lastname: Ellison
mesh_terms: D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D005663:Furans / Q000737:chemistry*; D013058:Mass Spectrometry; D046210:Microfluidic Analytical Techniques; D015394:Molecular Structure; D017655:Silicon Compounds / Q000737:chemistry; D013696:Temperature; D013997:Time Factors
chemical_list: D017554:Carbon Compounds, Inorganic; D005663:Furans; D017655:Silicon Compounds; C022088:silicon carbide